All animals must act in their environment in order to survive. They must also react to changes in the environment, for example, when threats or beneficial opportunities arise. Responses are defined as any reaction of the organism to external or internal events. Responses can pertain to one or more levels of body function ranging from cognition, behavior, and physiology to endocrine and biochemical reactions. The overall purpose of human and animal responses is optimal adaptation to environmental demands.
In sports, humans develop and hone sophisticated, explicit systems of action and reaction, often with the sole purpose of competing with one another. At first glance, athletes’ responses seem to be simple. A runner waits for the starter’s gun, and upon perception of the signal, she sprints as fast as possible toward the finish line. However, humans in general, and athletes in particular, respond in multiple distinct ways to action-relevant events such as a starter’s gun. In addition to a behavioral response, humans may respond physiologically (e.g., heart rate [HR] acceleration), emotionally (e.g., stage fright), and cognitively. An example of a purely cognitive response can be seen in athlete’s self-talk as a form of attention regulation. Moreover, humans respond not only to external events like a starter’s gun but also to internal events like psychological anticipatory stimuli. The latter can be seen in athletes’ false starts, where the signal is perceived in illusion possibly as a result of athletes’ internal rehearsal prior to the gun. This entry will first introduce a fundamental human response, the so-called orienting response, before describing more generally response characteristics and basic aspects of responses. Then, various response dimensions and response systems of the organism will be introduced before discussing the distinction between overt and covert responses. Measures are then presented that can be used to evaluate or quantify overt and covert responses. Finally, two specific aspects of responses, interference with performance and the value of covert responses, will be illustrated.
The simplest form of a behavioral response is the reflex. The Russian physiologist Ivan Pavlov was one of the pioneers in the investigation of involuntary reflex actions and classical conditioning, which is a form of learning. He believed that the involuntary reflex action is an unconditioned response—that is, it was seen as an inborn behavioral pattern. This reaction of the organism toward some relevant change in the environment could be described as the expression of curiosity and, accordingly, it was also termed the “What is this?” response by Ivan Pavlov. He defined three functions for this reflex: to activate the organism, to draw its attention toward the environmental change, and to prepare for the exploration of the associated section of the environment. Later, Evgeny Sokolov researched this response more systematically and gave it the name that is still used today, the orienting reflex.
Six different aspects of environmental events are known to elicit an orienting reflex or response, some of which may be interrelated: (1) novelty, (2) reaching a certain intensity threshold, (3) relevance of the event, (4) its associated surprise, (5) the event’s incongruity with the organism’s experience, and (6) an induced action conflict (i.e., if two actions are required with the same priority). The orienting response is known to habituate (i.e., with repeated presentation of the relevant stimulus, the orienting response becomes weaker). This is also known as the familiarization of the organism with the stimulus.
Responses are conceptualized as the individual inclination to react to external or internal stimuli. External stimuli represent events in the environment that can be perceived with the sensory organs. Internal stimuli are events that originate from within the body and can be either somatic or psychological. A full description of responses includes a description of the elicited change and also how long it takes until the reacting system comes back to the pre-response state. An individual’s inclination to react can be temporally variable or stable and may thus be conceptualized as state or trait-dependent.
Responses are seen as interactions of the organism with the environment—that is, responses are a basic way for organisms to cope with their surroundings. Responses describe the way individuals react to external and internal events. At the same time, responses also encompass reactions that influence the stimulus situation or environment. That is, responses reflect the influence of the environment on the individual but also the influence the individual has on the environment. Under such a transactional view, individuals can, of course, predict upcoming stimuli and the effects of their own reactions.
Four basic aspects of responses can be distinguished. One is the sensitivity of the organism— for example, the threshold at which a reaction is elicited, or the strength, latency, speed, or duration of the reaction. The second aspect is the adaptability of the organism to repetitive stimulation (habituation), or even constant stimulation (adaption). The third aspect is the resilience of the organism. Resilience refers to the manner, strength, duration, or continuity of the stimulation. Finally, the organism’s influence on the stimulus or the whole situation refers to changes in, for example, the source of stimulation, psychological processes (e.g., attention), or the whole situation in which the event occurred. These aspects also make evident that responses can refer to short-term or long-term reactions of the organism.
Responses can be related to different dimensions and to different systems of the organism. Stimulus related dimensions of responses refer to physical (e.g., loudness or brightness) and psychological aspects (e.g., threat or attractiveness). Responses can also be described by the dimensions of the reaction itself. One can distinguish, for example, the quality, the intensity, or the course of reacting (e.g., latency, duration, or habituation). Two additional important dimensions in the characterization of responses are temporal and situational aspects.
Here, we focus on a major division among different response systems of the organism. The major response systems are the somatic, biochemical and neurochemical, endocrine, immunological, and psychological systems. The somatic response system refers to the central and peripheral nervous system and to the muscle system, whereas the psychological system refers to perception, cognition, memory, emotion, action control, and so on. One major division that cuts across these systems is whether a response is overt or covert.
Overt Versus Covert Responses
Overt responses are characterized by the involvement of movements. That is, they can at least partially be evaluated by an outside observer. Overt responses include gross body movements like starting to run in a competition, small movements, such as shivering, and minor or subtle movements. Movement changes may occur inside the body—for example, by increased activity of the cardiovascular system (resulting in an increased blood pressure [BP]) and may be observed by, for example, changes in skin coloration (e.g., blushing). Covert responses, in contrast, reflect internal processes of information processing. By internal processes, we restrict ourselves here to the psychological system: processes of perception, recognition, memory, thought, action, and emotions. Movements do not constitute an integral part of covert responses. The dichotomy of overt versus covert responses corresponds roughly to bodily or psychological reactions and may serve as an approximation. For other response systems such as the neurochemical or endocrine systems, other classifications may be more appropriate.
Such a conceptual distinction calls for empirical support—that is, the question of how overt and covert responses can be measured and how such measurements differ arises. In particular, parameters are needed that can capture responses regarding their quality, latency, duration, amplitude, course of reaction, and their return to the pre-response state.
Overt responses involve some form of movement. Hence, they are prone to observation—that is, they can be evaluated by an outside observer. Such a form of measurement may require a subsequent, reliable form of movement classification. Depending on the research topic, one must define relevant movement categories such as, for example, running away, approaching an object, or preparing for action. More specific or “smaller” bodily movements can also be directly measured. The measurement of kinematic, or temporal and dynamic (i.e., force), aspects can provide detailed information about physical parameters such as the aforementioned latency, duration, amplitude of reactions, and so on, by measuring changes in joint angles or muscularity, for example. Such technical measurements provide objective diagnostics of overt responses.
In contrast, covert responses defined as psychological responses cannot be directly measured. To obtain information about covert responses, one can use the method of self-report, whereby the subject describes verbally their responses. Again, the description can relate to different dimensions of the response, such as stimulus or reaction-related or different response systems (e.g., somatic or psychological). Another, more objective measurement of covert responses can be acquired with psychological questionnaires. Information about the quality of the data, such as reliability and validity, are usually available with this measurement tool. Psychological questionnaires can be used to evaluate trait variables such as hand preference or achievement motivation or state variables such as state anxiety (SA) or emotional arousal. The biological basis of all such covert responses, at least the great majority, is seen in the central nervous system (CNS). As a consequence, the measurement of the activity of the CNS provides a powerful and objective, although less direct way to evaluate covert responses. Of course, the voluntary control of overt responses—action control—also involves the CNS. To measure activity in the CNS, one can record central or peripheral physiological parameters, as these are the closest correlates of psychological responses available to date.
Central Versus Peripheral Measurements
Measures of CNS activity can reflect the reactions of both specific and unspecific nervous subsystems. One example of an unspecific system is the ascending reticular activating system (ARAS), a neural network originating in the brain stem that is involved in the regulation of sleep–wake transitions. Its function is unspecific as it regulates the overall arousal level. Attention is another unspecific system that is supported by a front parietal network in the brain’s cortex because external as well as internal events from all sensory domains can attract attention. Examples for specific nervous systems are the (neuronal part of the) stress response system, which prepares the organism for strong bodily activity, the so-called fight-or-flight reaction; the motor system, with its neural circuits to both the basal ganglia (main function: selection and initiation of voluntary movements) and the cerebellum (main function: control and fine adjustment of movements), is another example of a specific nervous response system.
Depending on the method of investigation, one can measure various parameters of responses within the different functional systems of the CNS—for example, changes in an electroencephalograph (EEG) frequency band that is related to attention. However, it appears to be more difficult to relate recorded parameters—that is, EEG changes in our example to specific dimensions, whereby the dimensions could be either stimulusor response-related. If a particular EEG response with a given latency is recorded, such as after perceiving a starter’s gun, the response may refer to the stimulus (its loudness) to the emotional response (a startle reaction), or to the response preparation—that is, to run as fast as possible.
Today, CNS activity can be measured with a number of invasive and noninvasive methods that differ in their temporal and spatial measurement precision. Noninvasive techniques include the electroencephalogram (EEG) and the magneto encephalogram (MEG), which have a high temporal resolution. These methods measure the summed electrical (EEG) or magnetic (MEG) fields, respectively, of neural activity in the brain’s cortex. Functional magnetic resonance imaging (fMRI) and near-infrared spectroscopy (NIRS) have a high spatial resolution and measure indirectly through changes in blood flow nervous activity; fMRI can do so throughout the brain. Finally, an invasive technique that can only be applied in a patient or animal setting is the intracranial recording of electric fields or action potentials—that is, using recording electrodes implanted into the brain tissue during an operation. This method has a superior temporal and spatial resolution.
Another way to evaluate covert responses is to measure peripheral activity. Some measures of peripheral activity are very good indicators of central nervous processes—for example, the orienting response—even though the peripheral systems have specific peripheral functions. Furthermore, recordings are usually performed with techniques that are easier to apply than the aforementioned techniques for recording CNS activity. Useful systems for the evaluation of covert responses are the cardiovascular system, the electrodermal system—that is, by and large sweat gland activity—and reactions of the eye—for example, pupil dilation or eye fixations. The cardiovascular system—for example, HR—is a peripheral indicator of the activity in the sympathetic and parasympathetic nervous system (PNS). These important parts of the autonomous nervous system are implicated in the stress response. Both parts, the sympathetic and the PNS, normally show complementary reactions, and it is difficult to isolate one from the other. In order to measure sympathetic activity, electrodermal data is helpful. Sweat glands are solely innervated by the sympathetic part of the autonomous nervous system, and can thus serve as an indicator of the CNS functions associated with sympathetic activity. Eye movements, finally, are a reliable measure for various cognitive processes. They are informative for processes such as visual search—that is, the scan path of the eyes, reading, and attention. Visual search is an important process, for example, to capture the distribution of teammates over the playing field. Of particular interest is the pupil response—that is, a change in diameter that is associated with cognitive workload and affective processing. These peripheral measurements, especially eye movements, can be taken while the participant is fully mobile, which permits an investigation of covert responses in natural settings.
Illustrations in Sport Settings
In sport settings, humans aim for optimal control over their responses. This includes not only the production of wanted behaviors but also the inhibition and suppression of some unwanted responses. Specifically, responses ranging from involuntary muscle activity to psychological distractions due to stress can severely interfere with performance, particularly in competitions. The latter is known as choking under pressure. This phenomenon refers to acute performance decrements due to attentional malfunctions or perceived pressure to achieve. Another example of interfering responses are the so-called yips in golf. “Yips” are involuntary hand and arm movements—that is, jerks, tremors, or freezing that adversely affect the movement trajectory possibly involving a deterioration of the basal ganglia. Such unwanted responses can interfere with sport performance, and athletes must train to control them.
Covert responses also play an important role in sports, specifically in mental training. Mental training refers to the imagined reproduction of a movement sequence without any movement execution; it is a cognitive reproduction of the movement. This form of training can lead to performance improvements, especially for cognitive task aspects and if combined with physical training. It is thought that the activation of movement representations in memory below the motor threshold—that is, a covert response—is responsible for later improvements in movement performance. Thus, mental training is a form of covert response to internal events, which plays an important role in sport settings.
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